This has been one of the most contentious, polarising election seasons ever recorded in the USA. The US election season is lengthy and seems to begin unofficially up to 20 months before election day. Japan's election season is just 12 days long.
In February of election year, the USA's two main political parties, the Democrats and the Republicans, pick nominees through contests at the state level, this can take 5 months. In the USA there are no laws governing the length of the election cycle.